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MathGroup Archive 2007

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Re: Optimisation of FourierCoefficients

  • To: mathgroup at smc.vnet.net
  • Subject: [mg75250] Re: Optimisation of FourierCoefficients
  • From: Peter Pein <petsie at dordos.net>
  • Date: Sun, 22 Apr 2007 03:45:46 -0400 (EDT)
  • References: <f09gh3$12c$1@smc.vnet.net>

Edmund schrieb:
> I want to find the minimum of a Fourier-Coefficient as a function of the 
> input values.
> 
> FindMinimum[Abs[Fourier[{ y, 1}][[1]]], {y, 2}]
> 
> The actual problem is a little more complicated, but even this simple 
> statements gives the error messages I can't understand.
> 
> Fourier::fftl: Argument {y, 1} is not a non-empty list or rectangular array 
> \
> of numeric quantities.
> 
> 
> Any suggestion ?
> 
> best regards
> 
> Edmund
> 
> 
> 
Hi Edmund,

define Abs[....] as a seperate function for numeric arguments:

In[1]:= absFourier[y_?NumericQ] := Abs[First[Fourier[{y, 1}]]];
In[2]:= FindMinimum[absFourier[y], {y, 2}, WorkingPrecision -> 29]
Out[2]=
{1.1180339887499007107476283018*10^-15,
  {y -> -1.0000000000000015811388300842}
}

HTH,
Peter


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